1. Field Of The Invention
The present invention relates generally to apparatus for subjecting material, such as sheet material, to a predetermined effect, which may be a processing effect, such as heat. Specifically, the invention relates to such apparatus wherein the material, which may be in short pieces or in long lengths, is appropriately positioned adjacent to an effect-producing means in order to cause the latter to subject the material to the predetermined effect. More specifically, the invention relates to that form of such apparatus wherein the noted positioning of the material adjacent to the effect-producing means is done by a material-positioning member which has a surface in contact with the material, and which, in the course of causing the material to be subjected to the desired effect, may simply hold the material stationary with respect to the effect-producing means, or may move the material relative to the effect-producing means.
2. Description Of The Prior Art
Apparatus of the type noted above, including a material-positioning member which contacts the material in positioning it so that it is subjected to the desired effect, is known and used extensively in numerous fields and applications. Such apparatus is known and used, for example, for drying, coating, shaping, developing, or otherwise processing, handling, or treating many different forms and types of materials.
One of the more extensive uses of such known apparatus is in the sheet material processing field, wherein the positioning member contacts the material to cause it to be subjected to the processing effect, and often also drives or conveys the material along or past the source of the processing effect in the course of the processing operation. Although the present invention is applicable to such apparatus in general, wherever the material is contacted by the positioning member while being exposed or subjected to the processing effect, the invention will be described herein with specific reference to that typical class or form of the known apparatus which is employed to process sheet material, and specifically to process long lengths of so-called heat-processed sheet material or film such as that which is used as the record medium in certain known recording instruments.
In a well known form of the typical apparatus last identified above, unprocessed film of the above-noted type bearing a recorded image or record passes into contact with the surface of a heated rotating drum. The film is positioned and held in contact with the drum by a shoe device so that the film moves with the drum and is subjected to the heat of the latter. This heat processes the film so that the record thereon is made permanently visible on the processed film which leaves the drum at the end of the processing procedure.
Although the known apparatus just described is capable of providing the noted processing action, said apparatus suffers from an inherent practical shortcoming. Specifically, it is known that optimum processing of such film requires that it be heated to a given temperature for a given length of time. This time may well be of the order of 30 seconds. For a typical speed of 1 inch per second for the recorded film arriving at the drum, the latter must thus have an effective heated surface length of the order of 30 inches. This requires that the drum have a diameter of the order of 10 inches. It is this requirement which constitutes the noted shortcoming of the known apparatus, since this requirement precludes the use of the apparatus as a part of a reasonably sized recording instrument.
In an effort to avoid the noted shortcoming of the above-described known apparatus, it has been proposed in the past to obtain the needed length of heated surface by the use of a folded heated platen, and to use a moving, endless, compliant belt as the positioning member to bring and maintain the film into processing contact with the platen. In this proposed arrangement, which is similar to the known arrangements employed for drying sheet material, the film bearing the record passes into contact with a contact surface of the belt, which then drives or conveys the film over, and in contact with, the heated platen surface. As before, the heat processes the film so that the record thereon is made permanently visible on the processed film which leaves the belt and the platen at the trailing end of the latter. This proposed arrangement has the practical advantage over the known drum type of apparatus described above of requiring significantly less space, inasmuch as the folded platen provides the needed length of heated surface in a significantly smaller space than that required when the same length of heated surface must be supplied by a drum.
Although the proposed belt and platen apparatus as just described is of a more practical and acceptable size with respect to the earlier described drum form of apparatus, the proposed belt and platen apparatus has been found to posses an even more series inherent shortcoming, which has made use of the proposed apparatus impractical. Specifically, it has been found that, in the use of this apparatus, the texture of the surface of the belt which contacts the film is transferred to, and appears permanently on, the film, and thus obliterates or at least degrades the record on the film. Such transfer of the belt surface texture or pattern to the film has been attributed to inherent unequal film pressure and thermal loading, which result in an unequal processing action. Consequently, it has not been possible to employ this proposed form of apparatus successfully.